Known as conventional drive circuits for driving capacitive loads are sustain drives for driving sustain electrodes in plasma display panels, for example.
FIG. 16 is a circuit diagram showing the configuration of a conventional sustain driver. As shown in FIG. 16, a sustain driver 400 includes a recovery capacitor C401, a recovery coil L401, switches SW11, SW12, SW21, and SW22, and diodes D401 and D402.
The switch SW11 is connected between a power supply terminal V4 and a node N11, and the switch SW12 is connected between the node N11 and a ground terminal. A power supply voltage Vsus is applied to the power supply voltage V4. The node N11 is connected to 480 sustain electrodes, for example. A panel capacitance Cp corresponding to the total capacitance between the plurality of sustain electrodes and the ground terminal is shown in FIG. 16.
The recovery capacitor C401 is connected between a node N13 and the ground terminal. The switch SW21 and the diode D401 are connected in series between the node N13 and a node N12, and the diode D402 and the switch SW22 are connected in series between the node N12 and the node N13. The recovery coil L401 is connected between the node N12 and the node N11.
FIG. 17 is a timing chart showing the operations in a sustain time period of the sustain driver 400 shown in FIG. 16. A voltage of the node N11 shown in FIG. 16 and the respective operations of the switches SW21, SW11, SW22, and SW12 are shown in FIG. 17. An ON state and an OFF state of each of the switches SW21, SW11, SW22, and SW12 are respectively indicated by a high level and a low level.
First, in a time period Ta, the switch SW21 is turned on, and the switch SW12 is turned off. At this time, the switches SW11 and SW22 are turned off. Thus, a potential at the node N11 gently rises due to LC resonance caused by the recovery coil L401 and the panel capacitance Cp. Then, in a time period Tb, the switch SW21 is turned off, and the switch SW11 is turned on. Thus, the potential at the node N11 rapidly rises. In a time period Tc, the potential at the node N11 is fixed to the power supply voltage Vsus.
Then, in a time period Td, the switch SW11 is turned off, and the switch SW22 is turned on. Thus, the potential at the node N11 gently falls due to LC resonance caused by the recovery coil L401 and the panel capacitance Cp. Thereafter, in a time period Te, the switch SW22 is turned off, and the switch SW12 is turned on. Thus, the potential at the node N11 rapidly falls, and is fixed to the ground potential. A periodical sustain pulse Psu is applied to the plurality of sustain electrodes by repeating the above-mentioned operations in the sustain time period.
As described in the foregoing, a rise portion and a fall portion of the sustain pulse Psu are respectively composed of LC resonance portions in the time periods Ta and Td by the operation of the switch SW21 or SW22 and edges in the time periods Tb and Te by an on-operation of the switch SW11 or SW12 (see Patent Document 1).    [Patent Document 1] JP 3369535 B